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Fast and efficient ladder test.
#6821315
07/13/17 12:41 PM
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Joined: Dec 2008
Posts: 41,160
J.G.
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Randy obtained a new DPMS LR-308 G-2, with 20" Barrel. He decided on 165 gr Hornady boat tail spire point, and I said let's try IMR 8208, since it worked so well in my rifle that is similar. Simmons 4-12X with a duplex reticle. I checked zero at 100 with a copy of the lowest charge, then held the point of the heavy post on steel at 300 yards, since that distance from center of the reticle was exactly equivalent to 1.0 Mil. The bullet impacted low from center, but I knew it would keep us on paper, so that was my hold, on the "+" every shot. I do have a Razor 85mm spotting scope with a fixed 30X Mil eye piece. Randy stayed on the spotter while I shot 3 rounds through his rifle. Then I would get behind the spotter and "map" where each one landed, POI vs. POA in tenth of Mil. And write the powder charge next to the impact on the map. Photo below explains it well. We never drove to the target through 15 shots. We stayed parked in the loading room, in the shade. . . After the shooting, I drove out and retrieved the paper target. The bullets had been colored and labeled accordingly, so we knew what color bullet hole was which charge. We had a clear node at 40.0, 40.3, and 40.6 gr. Those three grouped 2". . I told Randy usually the one in the middle of the node is the winner of the group shoot, but let's not skip a charge. Well 40.0 shot 1 1/2" tall and 4" wide at 200 yards, then I shot 40.3" gr. 200 yards. Height is more important to me, but it was .58" wide. I just loaded the wrong photo here. That's 1/4 MOA in a plain vanilla DPMS. Will it do that every time? No way, but we did find the BEST powder charge after having shot only 22 rounds. This process took a grand total of 2 hours. Since Randy brought his press, and components prepared to load a group within the node, immediately after shooting the ladder test.
Last edited by FiremanJG; 07/13/17 12:48 PM.
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6821394
07/13/17 01:49 PM
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Joined: Nov 2011
Posts: 4,563
patriot07
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Very nice!
What distance would you do this for on a 223? 200 yards?
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Re: Fast and efficient ladder test.
[Re: patriot07]
#6821403
07/13/17 01:55 PM
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Joined: Dec 2008
Posts: 41,160
J.G.
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My personal minimum distance for a ladder test is 300 yards. And I have performed a ladder test, with a .223, at 300 yards. It worked perfectly.
I'm fact I have ladder tested the following cartridges at 300 or 500 yards, and every time it has given me the perfect powder charge. Frequently there will be a slow node (light powder charge) and a fast mode (heavy powder charge). The .308 AR, above had a clear winning powder charge, in the middle of the charge weights.
.223 .22-250 .243 6.5 Creedmoor .260 Rem 7mm-08 .308 Win (bolt action, and AR) 7 Rem Mag .300 Win Mag
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6821408
07/13/17 01:59 PM
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patriot07
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Good to know, thanks.
Do you have a chrono available for public use? Or do you not even worry about a chrono until you find the right load?
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Re: Fast and efficient ladder test.
[Re: patriot07]
#6821413
07/13/17 02:04 PM
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Joined: Dec 2008
Posts: 41,160
J.G.
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I've got a cheap-o Shooting Chrony. It's fairly accurate, but I get real velocity by working DOPE backwards into the calculator.
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6821414
07/13/17 02:06 PM
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patriot07
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Makes sense. Thanks for the helpful posts.
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6821683
07/13/17 06:51 PM
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J.G.
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6821718
07/13/17 07:32 PM
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Joined: Jun 2011
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Buzzsaw
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6822094
07/14/17 01:40 AM
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Joined: Dec 2009
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Big Fitz
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Very nice! I think your mapping needs improvement though...
I was wrong...on anything technical. Fitz............. is right, ya know............
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6822134
07/14/17 02:39 AM
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Joined: May 2017
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Smokey Bear
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Good work! It's always nice when things come together on the first go. I have only been loading 8208 a short while but it is rapidly becoming one of my favorite powders.
Smokey Bear---Lone Star State.
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Re: Fast and efficient ladder test.
[Re: Big Fitz]
#6822153
07/14/17 03:10 AM
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Joined: Dec 2008
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J.G.
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Very nice! I think your mapping needs improvement though... Next time I'll call you, and you can do it, then. Actually, the next time will be Tuesday or Wednesday. Wait by the phone.
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6822371
07/14/17 01:39 PM
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Joined: Oct 2004
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redchevy
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Maybe I'm understanding a ladder test wrong, but some of the results look odd to me. Were all rounds fire with the same point of aim?
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Re: Fast and efficient ladder test.
[Re: redchevy]
#6822402
07/14/17 01:59 PM
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OkieDokie
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Maybe I'm understanding a ladder test wrong, but some of the results look odd to me. Were all rounds fire with the same point of aim? Yes.
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Re: Fast and efficient ladder test.
[Re: OkieDokie]
#6822421
07/14/17 02:15 PM
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Joined: Dec 2008
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J.G.
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Maybe I'm understanding a ladder test wrong, but some of the results look odd to me. Were all rounds fire with the same point of aim? Yes. Yes. Hard to read this one since powder charges next to bullet holes are in pencil. In there, 3 loads grouped 2" at 300 yards. That's telling us between 40.0 gr and 40.9 gr is the node. Focus on that area and group shoot each charge.
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6822437
07/14/17 02:24 PM
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Joined: Oct 2004
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redchevy
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It appears most of your 38 and 39 grain charge weights impacted higher than the 40-41 grain charges, or am I seeing something wrong? I would have expected the opposite.
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Re: Fast and efficient ladder test.
[Re: redchevy]
#6822455
07/14/17 02:43 PM
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Joined: Nov 2011
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patriot07
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It appears most of your 38 and 39 grain charge weights impacted higher than the 40-41 grain charges, or am I seeing something wrong? I would have expected the opposite. I am running into the same thing on my Tikka 223. CFE223 with 25+ grains impacted well below the 23.5-25 grain charges. Really odd. My assumption is that the barrel is flexing downward for those heavier loads, but I won't pretend to say that's anything more than an uneducated guess. The hotter loads run 2800-2900 and impact lower than the lighter loads running 2650-2750.
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Re: Fast and efficient ladder test.
[Re: patriot07]
#6822499
07/14/17 03:43 PM
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Joined: Dec 2008
Posts: 41,160
J.G.
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The three lowest impacting shots were the first shot in the mag. Weird phenomenon of an AR. The last shot in the mag i can explain. The bolt locks open, robbing gas, causing a low impact. That's why we had another round in the mag that did not get fired, so the bolt would cycle.
Lesser powder charges should impact lower than higher powder charges, and I've seen that be text book with bolt action rifles.
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6822687
07/14/17 06:42 PM
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Joined: May 2017
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Smokey Bear
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Some refer to it as "barrel timing". When the gun is fired a shock wave much the same as the shock wave generated from TNT, races down the barrel. When it gets to the muzzle, some of the energy rebounds and returns toward the action. Doing the same at both ends till the energy is disapated. It is the modification of this effect that that we document and take advantage of in a ladder test. Tuning our charge so the projectile leaves the muzzle during a favorable cycle of this vibration. We refer to it as an accuracy node.
Smokey Bear---Lone Star State.
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6822780
07/14/17 08:11 PM
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Texan Til I Die
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The three lowest impacting shots were the first shot in the mag. Weird phenomenon of an AR. The last shot in the mag i can explain. The bolt locks open, robbing gas, causing a low impact. That's why we had another round in the mag that did not get fired, so the bolt would cycle. I see the same thing in my AR except the first shot from the mag is ALWAYS high and slightly left. Interestingly, the last round out of the mag stays pretty tight.
Silver spurs and gold tequila keep me hanging on. Pretty girls and old cantinas give me shelter from the storm.
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6822785
07/14/17 08:17 PM
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Joined: Oct 2004
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redchevy
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I'm just gonna stick to bolt guns, single shots, and my 10/22
It's hell eatin em live
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6823123
07/15/17 02:50 AM
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Joined: Nov 2011
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DStroud
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The lower charges impacting higher could be simply the slower moving bullets exiting the barrel later as the barrel moves upward due to recoil. Also while I have seen changes in POI on the last round fired as the bolt remained open it hasn't been necessarily lower and the velocity has been normally the same. I would think the bullet has exited the barrel well before the bolt is even halfway back? Just a thought.
"Anyone taking up handloading necessarily plays with unknown factors and takes chances. But so does anyone who drives a car,goes to a cocktail party,eats in a restaurant,or gets married."
Jack O'Connor 1963
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Re: Fast and efficient ladder test.
[Re: DStroud]
#6823169
07/15/17 03:49 AM
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Joined: Dec 2008
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J.G.
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Seen last round from the mag, out of an AR-10, go low many times. I am open for another explanation as to why this happens.
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6823359
07/15/17 03:16 PM
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DStroud
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Seen last round from the mag, out of an AR-10, go low many times. I am open for another explanation as to why this happens. If chronograph readings on that last round were constantly low then that theory would be plausible...... let us know once the research is done and data is available.
"Anyone taking up handloading necessarily plays with unknown factors and takes chances. But so does anyone who drives a car,goes to a cocktail party,eats in a restaurant,or gets married."
Jack O'Connor 1963
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Re: Fast and efficient ladder test.
[Re: redchevy]
#6823430
07/15/17 05:35 PM
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Joined: Apr 2011
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Cool Mo D
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I'm just gonna stick to bolt guns, single shots, and my 10/22 Me too.
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Re: Fast and efficient ladder test.
[Re: J.G.]
#6823491
07/15/17 07:19 PM
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Jgraider
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Seen last round from the mag, out of an AR-10, go low many times. I am open for another explanation as to why this happens. Good reason not to use one.
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